These are the very colors not separable by victims of the most
common type of colorblindness.

That's probably why they were selected.

My understanding of color vision is that (aside from the rods) there are
three different kinds of cones in the eye - each optimized for a
different wavelength. This is what results in "primary colors". So, in
a sense, the primary colors are "as far apart as you can get", and
people with normal vision should be able to tell them apart the easiest.
Thus they make a good choice for discernment, where "closer" colors
are less good.

Colorblindness (or more accurately "anomolous color sensitivity") has to
do with problems with these cone types, or sometimes the lack of certain
cone types. (There are individuals who have four cone types, they see
different primary colors, perhaps even outside our range of vision.)
So, if the problem is with the very cones we've chosen to make the
colors "as far apart as possible", then those two colors are
indistinguishable. There is, in effect, a lack of redundancy in this
color choice. I don't know whether or not this was considered when the
choice was made.

I've noticed myself that the green (in airport beacons) is often not a
well saturated green, and the green (on wingtips) is often blue.
Perhaps secondary colors would work better for colorblind people while
not being hard to distinguish for normally sighted people.

Jose
--
The monkey turns the crank and thinks he's making the music.
for Email, make the obvious change in the address.